Hi Barbara, You might want to call Roger at Eastwake Hardwoods also I know he has 12/4 and I believe he had some 16/4 not sure if he still does or not.
Barbara,
Drop me a PM and we'll work something out, I have a lot of 16/4 "carving grade" basswood. There's actually an entire truckload of basswood out in the shed, lots of huge slabs that are very wide (+16") and up to maybe 7' long, and all of it needs a new home because I don't have a use for basswood in my woodworking. I was thinking about posting it on here for sale or trade. If anyone else is interested, drop me a PM. After it warms up, I may drag all of it out of the shed and take some pics.