A year ago, I bought a 2018 Kymco XTown 300i. I've been frustrated with the lack of after market parts availability for this model.
I had hoped that K&N would have a filter for maybe another 300 model, that would interchange with mine, but apparently that's not the case?
In my frustration, I fabricated one, using a new K&N that I had in my garage for an old Suzuki TL 1000, and the stock filter.
I cut the paper element out and ground the surface down to bare plastic. Then, cut the much larger K&N filter to the exact same size, being very careful not to include any of the metal screening in the process.
Liquid Nails makes a construction adhesive called FuzIt, which is one of the best all around adhesive/caulks I've found.
After cleaning everything thoroughly with Acetone, I created a bed of the adhesive in the OEM plastic opening, then inserted the K&N filter element.
After re-oiling the element, I'm quite happy with the way it worked out.
