You may be better off looking for individual cassette cogs. Could be less expensive in the long run. I have a handful of new ones but not in a series to make up a correct cassette.
If you're looking to fill a DA 7 speed freehub, you likely already know that the first position cog has a smaller internal threaded diameter than other UG cogs. Finding that could be difficult.
8 speed 7403 hubs (which will also take 9 & 10 speed cassettes) that take HG cogs and a lock ring are out there, but they are expensive.
Additionally, 740X freehubs 1) attach to the hub in a completely different way than any other Shimano freehub, and 2) require a special tool that is hard to find and costs as much as a correct freehub. There are home-made removers posted here by previous forum members, would be worth searching if you are going in that direction.
Ultimately, my suggestion to folks who are interested in 740X groups is to go all in and buy the tools and spares, or not at all. DA 7700 is every bit as nice cosmetically and is compatible with pretty much everything else Shimano up thru 10 speed. Alternatively, you can use 7700 hubs (which are HG) for any 6-7-8-9-10 speed cassette and which will work just fine with 740X.
__________________
Hard at work in the Secret Underground Laboratory...