Baskerville Ultra is the best that I've found. It's made of sturdy plastic and can attach to their collar for added security. Petco sells them. http://www.petco.com/product/119470/The-Company-of-Animals-Baskerville-Ultra-Muzzle-for-Dogs.aspx
As for training it, just go very slowly. Start by letting him look at or sniff the muzzle and feed him treats (human food if he doesn't like dog treats. Tofurkey, peanut butter, cheese, whatever. It might take some trial and error to find something he really likes). Then you can start dropping treats (or smearing a little peanut butter) inside the muzzle, so he has to put his nose in to get it. Don't try to strap the muzzle on him yet. Tiny, tiny steps. Use really good treats, and after he eats a few, say "all gone!" and put the treats and muzzle away. You can do 2-3 minute sessions several times a day. Once he starts getting excited when he sees the muzzle and automatically sticking his nose in it to look for food, start feeding him treats rapid-fire through the bars as he has his face inside so he has to hold his nose inside the muzzle as he eats (still don't do up the straps yet! Have patience!). Once he is really good at holding his face in the muzzle for several seconds, you can drape the straps over the back of his head, feed him a really good treat, and then take the straps off. When he is doing really really well, you can buckle the straps, (only for a second at first!) feed treats nonstop while it is on, so he doesn't have time to paw at it, and then take it off. This is so much easier if you have 2 people: one to put the muzzle on and one to feed him treats through the bars. Slowly increase the amount of time he has the muzzle on. You can try asking him to do tricks, or taking for a short walk, so he has something else to focus on besides the muzzle. It's good to have him on a leash so he has to stay near you and you can distract him if he tries to paw at it. Don't yell no or correct him if he tries to get it off. You don't want him to have any negative associations with wearing the muzzle. Just get his attention (wave a sandwich in front of his face if you have to), ask him to sit or something similar, feed him a couple of treats, and take the muzzle off. It can take a while (weeks) for most dogs to get used to wearing a muzzle or head halter on their face. The worst thing you can do is rush it. He needs to learn that muzzle=awesome treats or play, and muzzle off=treats or fun stuff goes away. You want him to look forward to wearing the muzzle.
Hope that helps! It's what we do for the dogs at the shelter who have to be muzzled for vet visits. I'm sure if you google "acclimating dog to muzzle", you can find more info or videos.