If there is a Petsmart or PetCo in your area, I know they carry them. Check local pet supply stores. You might be able to find them at party supply stores(although in my experience they look at me like I'm an idiot when I ask where they are). If nothing else, search Amazon. I've found them there as well. =)
You know....as terrible as it is...I find that some dogs just don't want to do certain tricks. I have three puppies and each of them have a specific trick that the others won't do. My Luci will Bow and her litter sister Josie REFUSES to even bend her head! Whereas Josie will stand (two legs) and Luci things that isn't lady like, lol. Then there is Jasper...my big lug...he'll do high five (he actually hits your hand in the air) but the girls will barely do shake! I've given up on some of them. Either they are too stuborn or I am too lazy but I just don't think it's worth it to fight with them over something trivial.
see if you can get your dog to lift his paw off the ground and touch your hand, i got storm to hit my hand by blocking his view of me and he would lift his foot to get my hand down and i would reward
you could try give them a break from a certain trick and go back to it when they mature abit, some dogs seem like they dont want to learn a trick but they might just not be ready for it and they'll love the harder tricks and go back to simpler tricks later
If you are teaching her shake, command her to sit. After she sat down, sit down in front of her, and touch her paw, and reward her (if you get a clicker, click, reward). Then if she gets used to the idea, that you are touching her paw, raise it higher and higher (in small steps of course), while saying the command to shake. practice this for a longer time, until she is comfortable with her paw in your hand. Then just try to go back to the beginning, but now don't touch her paw. Say shake, and wait. If she doesn't do anything, then touch her paw and reward. If she does,(even a little movement of her paw is good, this way she will understand that she has to put her paw into you hand) then just put your hand higher and higher, until the real shake trick.
Or at least this is what I would do.
Please tell me this wasn't to messy, and you understood it!