There's a set of 1.25" LRGB filters listed here -
https://www.iceinspace.com.au/forum/...d.php?t=198175
If that blows your budget let me know, I literally just bought a set of the ZWO LRGB but might be persuaded into letting them go so I can upgrade to the astronomik, just shoot me a pm to chat about it if it interests you