My current popping strap (and why do they call it a strap?) is about 6" x 8" (15 x 21 cm). It works but it seems a little small to me compared to what I see other players use. So got a hold of a larger piece of leather. I want to cut it into a more common or traditional size/ shape.
Any suggestions?
For Concert Pitch pipes, the tradition dictates that no popping strap is allowed. Instead, the piper must cut a hole in the leg of his trousers and close the chanter on the bare skin of his thigh.
But seriously, whatever you find is comfortable. When not piping, my popping strap covers the regulator keys to prevent them from snagging anything in the case. For that reason it’s about 12"x12". Before I had a full set, I used a smaller strap, about 4"x8".
As you get more experienced you get more accurate placing the chanter on the strap and may need only a small one. As a relative beginner I suggest you use something like the one below.
RORY
That’s about the size of mine. My wife just hemmed a scrap piece of sueded leather we had laying around. I only use a few square inches of it anyway, the rest is just so that there some friction so it stays on my leg, though the drones and regs laying on one edge of it helps too.
Looks like Liam O’Flynn just folds up a car wash chamois and uses that, if you really think bigger is better. 
I use a good, thick piece of leather, about 10" x 11". It is long enough do drape over my thigh. I use it shiny side up, rough side down. Thus a marriage of gravity and friction keeps it in place.
rory beat me to it. 
How about a strap that looks like a flattened frog, limbs all splayed out, tongue protruding towards the audience, X marks for eyeballs? Lots of possibilities here.
Thanks Rory! Needed a good laugh!
haha nice one Rory x)
Seriously, it depends if it’s for a flat chanter or a D chanter? For a flat chanter the leather should be 3-4 millimeters thick, whereas for a D chanter no more than 2 millimeters thick. The overall size of the popping strap is not so important as long as it is larger than the diameter of the chanter bell.
I’m curious as to how you figure that - I play C natural, narrow-bore D, and wide-bore concert pitch chanters, all on the same thin suede popping strap. It can’t be more than 2 mm thick, though I haven’t measured it with a caliper. I’m thinking that as long as it makes an air-tight seal against the mouth of the bell, it doesn’t matter how thick it is (or isn’t).
I showed this to my wife… She wants me to get it. 
I ended up cutting a piece that is about 8" x 11". It stays on my leg better than the smaller piece.
That makes me as cool as Liam O’Flynn. I also use car wash chamois, as I have a habit of leaving popping straps in pubs, and car wash chamois can be easily bought at most garages. So I can replace lost ones no bother.
“I’m curious as to how you figure that - I play C natural, narrow-bore D, and wide-bore concert pitch chanters, all on the same thin suede popping strap. It can’t be more than 2 mm thick, though I haven’t measured it with a caliper. I’m thinking that as long as it makes an air-tight seal against the mouth of the bell, it doesn’t matter how thick it is (or isn’t).” An Draighean.
If the popping strap used with a D chanter is more than 2 mm thick it can affect the top d. The top d becomes flattened as the dampening affect of a too thick popping strap reduces the frequency of the wave lengths resonating down the bore upsetting the tuning of the top d and second octave notes. This can however be compensated for by using a light coloured popping strap, beige, white or pink for example. A wide brimmed hat can have the same effect if worn together with a tie.
Re: chamois. I see many respected players use them…but are they not too thin so as to fold, bunch up or crease?
Am I respected player now? Just kidding.
On a more serious note, you’re right and they are in fact shight as they do fold or bunch up and crease. They’re just easy to acquire and work well enough to get by. I once had a beautiful, smooth, perfect bit of leather. And then I left it in a pub somewhere. So I decided to put up with the lousy, but easily replaced ones.
@Steampacket. Does wearing a light-coloured shirt help? And presumably you’d want the right sort of pants as well (the British meaning).
I use the 10"x10" leather pieces from Michael’s Crafts. You can get them with one side smooth, cost is about $7.00.