Shops I Recommend

-InsectArt (Etsy), unmounted insects

-Little Caterpillar Art (Etsy), unmounted insects and supplies

-Little Lauren Arts (Etsy), unmounted insects

-BicBugs (bicbugs.com), unmounted insects I'd do a quick Google search before you decide to use them. Personally, I only use them for very specific things I can't find anywhere else.

-Oddities Marketplace, Facebook group
You can pretty much find anything you're looking for on Facebook, but this group always seems to have the best variety. You can do a search within the group to look for what you need or make a post. People are also very helpful on there and you can find other amazing artists. 

-Craft stores like JoAnn and Michaels (we don't support Hobby Lobby here), Supplies
I use Gorilla Glue hot glue and have about five hot glue guns. You can usually find a coupon code online if you pick up in store for at least 20% off. I sometimes just walk through the store to see if something random in there sparks inspiration. 

-Thrift stores and eBay!!, cool frames and vintage stands

-Supermoss (Supermoss.com), preserved moss
This is just what I do. You can find smaller bags at the craft stores I mentioned, but their site will let you choose a bulk option and give more variety. I know plenty of artists who like to forage moss themselves as well and it looks more realistic!