Hi, Nikki -
Bee Thinking sells a nuc that has the same dimensions as their TBH, although it’s just the box (no bees / not established). With the nuc, you can either set up a swarm lure, or take the box with you and seek out swarms in your area (put your name on lists with local pest control companies, and list online).
Capturing a swarm is not as hard as it sounds - there are lots of videos of how to do this online, and it works pretty much as advertised. This has a few advantages over packages, along with a few risks. The advantages, in my opinion, are that you are likely to get healthier stock - a split from a hive that was strong enough to cast off a swarm - and that you can do this any time during the season - although there are many more swarms in the spring, strong hives will continue to cast off swarms through the fall. Of course, the later in the year you get the swarm, the less likely they are to establish in time to successfully overwinter. The risks are mostly around the unknowns - is it good bee stock, honey producing, not aggressive, and how old is the queen, among other issues. But I have been pleasantly surprised by how docile and productive all of the “feral” swarms or new colonies are that I’ve seen in my area, and it’s easier to re-queen than start from scratch, so I think it’s worth trying.
If swarm-chasing is not your thing, you can install a package of bees into a TBH, much like you would with any other hive. If it’s your first TBH, though, you are probably at somewhat higher risk of the bees absconding (since you won’t have any established brood comb you can use to entice them to stick around).
I recommend the capture route - “buy local”!