The brake pads say F10BS but they've been really hard to find (and unavailable on Tektro site). Does Shimano (or anyone else) offer a resin version of this brake pad as this one is metal-ceramic?
Tektro has on their website a Brake pad finder tool. Entering your brake model number offers several compatible brake pad models. There are options for both resin/semi-metallic and metallic compounds. The above linked page has itself a hyperlink to an option of buying pads direct from Tektro.
Yes, Shimano brake pads can also be used. Your Tektro pad model numbers that can be used with the HD-R290 brakes are E10.11 & A10.11. Shimano brake pad model numbers that can replace these are B01S and M05. Tektro's higher performance pad option is model number P20.11 which can be switched out for Shimano's G01A, G02A, GO3S, & G04Ti. There are a couple other Tektro pad models that can be used with the HD-R290 (see results of the pad finder), however those models aren't listed as having a like Shimano pad.
TLDR: Shimano K03S or Swisstop Disc 34.
The HD-R290 brakes spec sheet does not indicate the pad to use - except that it must be resin, but finding subsitutes to the F10BS is possible.
According to Tektro website, F10BS are meant for HD-R310/R510 calipers. The compatibility chart on Tektro's site also states that the equivalent of these pads are Shimano K02S (resin, predecessor of K03S) and K04S (metal, excluded as indicated by the spec sheet).
Swisstop also indicates that they sell a brake pad compatible with these calipers: the Disc 34 (different variants, RS depicted here).
Note that I found a page that makes an explicit link between HD290 and the pads that I mentioned: the Cowboy 3 user manual, where the following is written:
The brake pads used on Cowboy bikes are the TEKTRO F10BS/F10XS but compatible pads include:
- TEKTRO HD-R290 brake pads
- Shimano K03S resin brake