As mentioned, legitimate Yaesu amateur radio gear is sold through dealers authorized by Yaesu USA. Among them are Ham Radio Outlet, DX Engineering, GigaParts, MTC Radio, R&L Electronics, etc. Unfortunately, the "Find a Dealer" tool on Yaesu USA's website doesn't simply list all of the authorized dealers. You have to search based on your location which might miss an online dealer.
For the most part, someone selling "Yaesu" radios on Ebay is not an authorized dealer (unless it's a store being operated by one of the authorized dealers). The FT-7900R was discontinued a few years ago. None of the dealers listed above have them in stock which should give a buyer a hint that a "new" one popping up on Ebay might not be a legitimate Yaesu radio.
"FT-7900R CHN" is plainly visible in the photos attached to three of the Ebay listings that I looked at. Note that those listings were from different sellers, but the ads read the same and had the same photos. This is a shell game that rip-off artists on Ebay play--they set up multiple accounts all of which sell the same thing and they aren't sharp enough to make the ads look different.
The watchword for buying from Ebay sellers has always been caveat emptor.