There are a lot of routers that are supported... You can look at this link to help select one:
- I want to buy a router which is supported by OpenWrt
There are also discussions such as this one and this one and many others in this category that may help you find a good router for your needs.
You can find many good, relatively recent routers available on the used market (depending on where you are in the world, the sites may be different -- but eBay, craigslst, facebook marketplace, etc. would be some in the US). You can also buy new devices in many electronics/computer stores online or in retail locations.