I bought one of these back in Feb to control my MOD Dwarf.  It is solidly constructed, nice and small, has a built-in rechargable battery and is only about £30! https://www.amazon.co.uk/SHUAIGUO-Chocolate-Wireless-Controller-Rechargeable/dp/B0B6PG9JK9 It can take a TRS expression pedal and send to midi,  it can send midi over usb or bluetooth, to do the latter they sell this (£18) https://www.amazon.co.uk/dp/B0B37M62BB/ref=sspa_dk_detail_3