Ebay, Aliexpress.
Generic chinese endmills and drills are very cheap, and the quality is perfectly fine. I've never received one that was chipped, dull, poorly ground or had any measurable runout.
On the other .038" is about 1mm, so this can be bought as standard accessory for Dremel or Proxxon. The shank on those is 2mm IIRC, but the collets are 6mm OD, so if you have bigger tool like Kress FME or something a 6mm or 1/4" collet will work.