A Hoover white cap will fix all that. And the white cap also does well on the even cheaper two-piece Clare — a perfect pocket-whistle. Put Mack back to work!
On my trip to Ireland I saw these cool little whistles that were meant to come apart inbetween the third and fourth hole, and would easily fit in any pocket, I remember them being something around 5 euro. I played a bit on one, sounded like a decent generation. I’ve been kicking myself recently for having not gotten a few of them.
Edit to MT: Thanks, I didn’t get the name of them, sorry bout that.
That’s the Clare 2-piece, mentioned several times above. 
a harmonica
Eh, I have a nice Lee Oskar harmonica, can’t make heads or tails of it (if anyone wanted to trade me a whistle for it…)
I’ve never tried an Oak before, but the price is right. Might go with the Whitecap-ed Oak idea.
what key?
it’s a diatonic key of C (with the case, if you’re interested)
I love the sound some people can get out of them, but I’m going to stick with my logical fipples.
thanks TB , I kinda like the key of A, or G thanks anyway
To combine two good ideas, the neat little case Carey sells for the Walkabout has a belt loop. 
http://www.parkswhistles.com/Accessories/WABWhistleCase/Default.aspx
Just to ally any fears about the durability of PVC whistle parts, here’s an email I received from a customer in Italy:
http://parkswhistlesblog.blogspot.com/2008/08/every-whistle-survives-day-on-street.html
I would also highly recommend the Parks walkabout. It is extremely sturdy and with the little pouch thingy already mentioned it will fit in either your pocket or on your belt. Great little whistle.
I take it traveling and enjoy it in Hotels in the “quiet” mode.
Best
Rod
Best whistle for sticking in your pocket? Depends how big an effect you want to create. 
[somebody had to say it]
“had to” is not correct because in this day and age compulsion is merely an option
You can also make a sturdy case for your Feadog from PVC pipe. Glue a cap on one end, glue a threaded adapter with a plug on the other and, voila, an almost indestructable whistle tube. Tie a cord around it and hang it on your belt.
David O’Brien used to make copper whistles that are almost weapons-grade. I have one of his Rovers that breaks into three pieces and came with a handy pouch. Very nice playing whistle but, like most heavy copper whistles, it clogs fairly easily. David’s site no longer lists copper whistles.
Are “Laughing Whistles” still being made? As I recall, those were telescoping conical brass whistles designed for fitting in a shirt pocket.
Bill W use to offer a whistle made of chromoly tubing. 
That is the same tubing that is used in high pressure boilers. He was in Oklahoma then moved east toward Virgina I think. Some buyers of his whistle use to brag of using it for a cheater pipe on a wrench with no distortion. Chromoly tubing is also used in making double AA fuel dragster frames and Indy 500 car frames.
pvc pipe with corks from wine bottles. Push the cork in all the way at one end, and that’s the sealed end. at the other end push the cork in half way and that end is your operation end for entry and egress.