You might be able to find that on AliExpress, I don’t know how to search that site for specific stuff and most of the unique things I found I just happened to come across, but it’s still worth taking a look.
Though you should know that quality is hit or miss, I’ve come across high quality sets with weird defects (stem is too short and the keycap hits the top housing) or the shape is fine but the legend thickness was all over the place, so I’d take a close look on the photos and reviews.
I second this, Syruplabs are great and they won’t jerk you around if you’re missing a single cap or two from your order. 10/10 recommend!
Another set with us-international sublegends:
KAT Napoleonic “Waterloo”.
It even has an EurKEY version named “Blücher”.
I am tempted, but I’m not sure I’d like the font… 
I also asked Signature Plastics if they would consider making a dsa set with us-intl sublegends. I’ll keep you posted what they say…
Would be amazing, since I love dsa.
Cool but kind of annoying that kits like Tulip actually include the “tulip” keys this time were R4 did not. 
Just as a matter of interest, have you tried the Eurkey layout? It has wider coverage than either US or UK international layouts.
I did try EurKEY, yes.
In fact I would prefer it, just for it’s wider coverage.
But there is just this one keycap set with it’s sublegends.
With us-intl you have at least some choice.
And since the languages I have to write on a daily basis work perfectly fine with us-intl, I’ll stick to that until I might get a greater variety with EurKey in the future.
They said that they considered and that they are already working on a design…
Is that customer service or what?
Amazing, I think! 
In case you (or anyone else) is still looking, these keycaps are marketed as “Irish” keycaps for some reason.