You’re probably talking about the ones lettered B in this Hatsan lightning compressor rebuild kit that tuxing sent me awhile back, when I inquired about sizes. Seems to me they said those filter tower ones were of viton, also. Unlike most o ring vendors that list the o ring sizes as the first number being the ID, The sizes shown in this pic the first number called out is the OD, second number the thickness. I emailed them to verify this, btw.
This should also be a kit close enough for the AV 4500 model, also.
Pull the one off of your gold tower and see if it is a 36mm ID x 2.5mm thickness
If you need this particular kit go to Tuxing.cn.com and you’ll see this along with other seal kits for the Yong Heng single cylinder type or the Tuxing twin cylinder types