In terms of sites/marketplaces that will have listings meeting the low 5-figure criteria, these two will likely be your best bet -- though because they do deal with a lot of lower value sites, there is a lot of lower quality and "starter" sites that you'll need to filter out.
https://www.sideprojectors.com/
The following sites generally have listings starting at low-to-mid 5-figures and you'll even regularly see 8-figure listings on them too. Some of these will also require you to sign NDAs before getting further information on a listing, but there's usually enough information on the overview for you to decide whether or not it's in the category/style of purchase you'd be interested in.