If it was me, I'd talk to my local Toyota service center about the possibility of swapping out a battery pack salvaged from a scrap yard. But frankly I think that's a long shot. In general, neither auto manufacturers nor auto dealers are interested in helping you refurbish your old car; they want to talk you into buying a new one instead.
And going to a third party for swapping out the battery pack would, I think, put you into the situation of having a car no more reliable than a conversion EV. Without Toyota being involved in swapping out the pack, there's no way to be sure that the BMS (the electronic Battery Management System) would be properly programmed. That would be a crap shoot as far as the car functioning properly, and also a crap shoot as to how long the car would last before a major malfunction left you without a usable car.
Sorry to be so negative, but the more complex they make cars, the harder it is to be able to rely on a third party for reliable maintenance. Unfortunately, the era of the "shade tree mechanic" has long passed.