Hey supply shops might work for pipes but I think their main customers are the PYOP shops and I think they would be a bad fit from what I know because its model is built mostly around events such as birthday parties so the supply shops might not be very interested. If they aren't you could try to go directly to studio potters who hand paint. There are some who buy tiles and such to paint and they become a good customer.
Since you say thousands I assume you have a good mold situation and now can cast them pretty quick and want to ramp up some more. Not sure how many pipes other potters are going buy but it might not make much of an impact. I can think of lots of end markets for finished pipes but not sure who the end market for bisque pipes would be that would generate any real numbers.
Good luck! Let us know what you find.
- JamesP likes this