New: a Stromberg NA-S3A1 carburetor for a C90 on eBay, Niceville, FL ($600). The prop-struck C85-12-F at 816 SMOH listed on eBay ($2,700) is also in a Facebook group at $4,050, which shows it is in Texarkana, TX; both prices are on the row. Nothing left the market and no asking price moved.
Sources checked Nov 2, 8:00 AM Central: Trade-A-Plane, Barnstormers, eBay, Controller, BAS Part Sales (formerly Wentworth), Craigslist (21 centres, 500 mi), Facebook Marketplace (14 stops, 40 mi), Facebook groups (12 picked by Rusty). Not reachable this run: AircraftForSale and GlobalAir (bot check on AircraftForSale search; GlobalAir has no engines section; not clicked through).
A part is listed only when its ad says it is for, or fits, a C-85 or a C-90. Each ad's own words are shown; nothing is inferred. Nothing here is this site's opinion.