I was going to suggest the Vex29 BB controllers at ~£8 but they seem to be out of stock and will be for a while. A lot of beetleweights use 10A reprogrammed Botbitz controllers. Used to be available through Ranglebox in the UK but haven't been in stock for a while. However, you can still get them direct from Botbitz; they come from Australia but the shipping can be quite quick and the service is good.
https://botbitz.com.au/collections/a...eed-controller