I purchased the Launchkey Mini mk3 because of the template for the RK-008 but didn't like the keys so returned it.
I purchased an M-VAVE Chocolate bluetooth midi footpedal but it wouldn't connect with the RK-008 despite trying all possibilities so I returned it.
I purchased the Korg nanoKEY studio as Gerrit told me it was used when developing BLE for the RK-008, it was ok-ish and with the Korg Kontrol editor enabled me to control 8 synths and drum machines via Bluetooth, but I never really got on with the little keys one of which stopped worrying properly.
Last week I purchased an M-VAVE smk-25 bluetooth midi keyboard with built in battery, stupid cheap on aliexpress, 8 programmable scenes, the pads are very nice and responsive, currently enjoying playing my Roland TR-06 with them, and it connects via bluetooth with the RK-008 no problem, sustain in can be configured as a regular midi out.
You can download a midisuite software for it but it turns out I am the only person who has ever tried to program and save the transport play stop and rec on a midi channel other than channel 1 as it wouldn't save, I reached out to mvaveofficial via insta and they had a new fixed midisuite up for me the next day.
I'm not trying to shill this keyboard but it works well for me.