First off, I must thank Care-In at Sweet Brown Sugars for posting pictures in the first place. She has been making bentos for her girls and gave me a wealth of ideas to share with you!
I bought my Sassy boxes at Babies R Us, but have been told they are also at Target. They come in blue and pink. I bought my Dr. Sears pineapple bento at HEB (a local grocery), but they are also on amazon.com. I bought my goodbyns from gilt.com, but you can find them on goodbyn.com or amazon.com. I have yet to use the goodbyns, but I'm looking forward to it. I love all of these for various reasons. The sassy boxes are small, but great for my 3 year old. It fits in his lunch box. I can give him a variety of foods. Everything is separated by airtight boxes. Same with the Pineapple. It is smaller, shallower, but I was able to get a good amount of food in there and the leaves come off and freeze!
My divided plates are all from Target, but not new. I buy things like this after Christmas or Easter at 50-90% off. My plain muffin tins are from our local grocery. My bear muffin cups are from Hobby Lobby. I just got blue stars and green circles from World Market and they had more girly ones...red and orange flowers I think. Hobby Lobby also has a set of pink and yellow flower muffin cups.
I have bought all my Japanese items on ebay. I used these two stores.
http://stores.ebay.com/SAKURA-ZAKKA-SHOPMake sure you buy from one store, ask for a invoice total and they will combine your shipping. From these two sites, I bought picks, mini forks, egg molds, mini sauce containers, and more picks.
My silicone cups are mostly from a Wilton train cupcake cake set. I used it for my oldest's 3rd birthday and love all the different shapes.
On to my cookie cutters...I have a few sets that I have had forever...bought after a season sale thinking when I have children, I'll make cookies. I have sets of hearts, snowmen, and Fall leaves. To add to that my mom let me go through her stash and I found a star, gingerbread man, snowflake and a dog. I found a mini duck and bear and a big car at Hobby Lobby. My stencil cutter set was bought on amazon.com.
Hopefully this will get you started. You can go to your local grocery and get a couple ziploc containers, a package of cookie cutters and start from there...it's really up to your imagination how crazy you get!