injust looked and couldn’t find it but they also sell a custom adapter with 1/2 threads that replaces the plastic ldc. Then you can ad whatever you want that will work better than that stock garbage.
If you don’t mind sourcing your own o rings and making a kit, here’s all the sizes for a 22 cal urban I put together for a friend, by pulling the dimensions off of the o rings in that same kit.
With the minute amount of o rings that the gamo urban has, I’d reseal that thing once a year, ha ha. Definitely way less than an Impact!