I’m going to use an example of a different site I used to browse a lot. Scorehero.com and bandhero.com actually have a smart way of linking their sites they have which is by a little logo of the opposite site at the top of the page. I think you could do something similar with this approach, and this could allow you to either get your own of a different domain, add on to your existing (such as highscore.speedrun.com or similar), or even the one you’re trying to buy. This will make it clear that these sites work together, and people can choose at that point for which they want to browse. Ideally option 3 is great, but if not then make use of your current domain or make a different one entirely. Maybe in the future that person will be more willing to make a deal with you if not now.