All I've had to do to get my grips is
go to this website
sign in, and enter your models serial number and such, do whatever you need to do to register to the website, and to register your iPAQ, then continue to the case manager, where you can enter a request. I basically just put "my rubber grips are coming off, this is the part number, send me another pair! Thanks!"
I have about two extra pairs, but the ones i have on now seem to be lasting a good amount of time. I have no problem asking for more, because they are free, and well I accept that they're crap but I don't have an extra 35 dollars for good grips.
This is just another option.
btw, im not sure if it works if youre iPAQ isn't under warranty anymore, i dont know how it would work in that situation, but yeah, it's always worked for me.