Electric drum kit question

[Jonboy_t]

I've been playing drums for years - about 25 now - and have just been very generously given an electric kit by a mate. It's a Yamaha DTXpress III, but is a bit of a mongrel as things have broken and been replaced with 'make do' bits, like the hi-hat which is just a normal drum trigger pad rather than a cymbal or hi-hat specific pad. It does me for practising at the moment though!

My question about it is, as and when I come to upgrade, expand or replace bits and bobs, do I have to have the Yamaha specific pads or can any fit? My guess would be that any are fine as long as it takes a standard jack lead?

Have tried googling etc and end up with manufacturers pages which clearly only plug their own gear, so thought I'd try you lot