Wanted- Post mount front disk brake caliper and lever

I'm converting my SS hardtail back to gears for the Gong ride, and since changing the fork have not run a front brake.

The new fork only has post mounts, and hence I am looking for a cheapy second hand disk brake to suit. I'll consider anything really, but would prefer hydraulic.

I can't justify getting new gear as I really only use this bike for chasing my kids around the streets.

Anyone who has anything PM me or call my mobile which is on my profile.

TIA,

Nick