This may be of interest for those looking for either a 1.25" or 2" UHC
I have found
these UHC filters quite effective on increasing the contrast and extent of nebulosity visible at least on the Orion Nebula through an 8" Dob.
There is a link to the bandpass specs with the filter listing.
And yes (in the interests of disclosure) I am selling these filters, which are the same spec as those sold by "Orion"