After checking this site
https://www.bike-parts-kymco.uk/kymco-motorcycle/300-SCOOTER/X-TOWN/XTOWN_300I_ABS_EURO_4/AIR-FILTER-BOX/204/5/0/204Which shows the part number in detail including what bikes it crosses to I'd say that it doesn't fit anything else (I checked the People 300 as well, different PN & showed a couple other bikes that it fit).
I did check BMC (like K&N but not them) as well. Sadly they didn't have one either, but they're probably more likely to come up with a filter for the X-Town than K&N.
If you want to go reusable I think you'd have to clean the paper out of your current frame and either nab a chunk of paper filter from a house filter or car filter (cheapest route) or nab some of the filter foam (a bit pricier and you need oil too), cut your material of choice to shape and glue it in place or find some other way to make sure it doesn't suck through (burgman filters have metal screen on one side for instance).
All depends on your craft skills and budget. There are folks in the Burgman world still reusing their old frames with car/house filter material even though you can now get cheap aftermarket ones.
Do remember that with current tech...TANSTAAFL. The more air flow through the filter, the less filtering it does.
If you google around a bit you'll find some real world testing using K&N filters (Where the testing was not done by K&N) that show this.
Real world impact for power or longevity no engine? Probably minimal either way is my hunch long's you're not in a real dusty environment.
OK, I guess another long shot. I'd like to replace the OEM air filter with a K&N.
Does anyone know if the airbox on the XTown 300i is the same as any of the others, possibly Downtown 300, or People 300??
I contacted K&N and they have no separate listing for anything XTown 300i.