Just throwing this in although I know you were asking about where to buy them and have already gotten them. We have 3 different popsicle trays, a smaller one with 8 (that was a "cheapie" no name brand thing I cant remember where I got several years ago), a "nicer" one with 4 and the popsicle holders have straws to drink the melted drippings that collect at the base of the stick and a big awful one that I think I ordered from somewhere. This big one also has 8 and the mold part of it is layered in 3 sizes (tip thin, middle medium and base is thick) and then you put a metal cover over it and it has slots for popsicle sticks - which I thought would be cool, since it is SO annoying when a popsicle stick breaks. BUT!!! you have to place the popsicle sticks ALL at the exact same angle so that you can lift the lid off in the first place!!! So I never use that one (it is also too big/tall to fit on the shelf in my freezer I usually use for popsicles)
My favorite one is the little cheapy one I got because it is small enough for my son (and small enough for my husband to have two!) What I did with having the 4 covers broken and only 4 covers still existing was have my husband cut it in half! So now I have two small '4-packs' that I can fill, wash and replace more frequently, using either popsicle sticks or the red popsicle sticks.
What we do around here is I make smoothie shakes - especially handy when I've got a lot of fruit on hand (mainly bananas, my husband wont touch them once they get a single freckle on it!) I throw bananas in, fruit (I keep frozen strawberries/berries in the freezer for this! if not using frozen, add ice as well), a scoop or two of lemonade or orange(tang) drink mix (OJ is better but I dont always have it ready made in the fridge), add ice/water and I am finding that is all it takes to make a good smoothie! My husband LOVES it and I am lucky if I have enough left to put into popsicle molds after drinking it! My son likes the popsicle smoothies but not drinking it.
Milk bothers my husband's stomach (he is ok with all other dairy though) so it has been nice to find that adding 2+ bananas balances out the citric acid from the OJ or drink mix without needing milk.
Of course you can always add plain old OJ, drinks, koolaid, etc. Even plain ice popsicles are good for teethers or mouth owies.