There is quite a decent one designed and made by someone on eBay which sells for about $190. Low and adjustable current, adjustable magnetic stirrer, although I think you could purchase a separate stirrer/hotplate if needed but it has no connection for such a device so it would need to be run separately. That might allow larger batches to be made but the built in stirrer might do larger than the standard amount by using a larger container with a different stopper top. There might be rubber bungs available for large mason jars.