You can find a group of Saraev varieties at Tania's - Tatiana's Tomatobase. I haven't grown them yet myself.
Cold Set and Siletz are both very small plants suitable for growing under a 4 ft hoop. They weren't that early for me but they certainly set in cool weather and tolerated a few cold nights. Fruit taste was quite decent for both of them - but split like crazy. Jagodka is also a very small plant, pretty small fruit for me and very tart in cool weather, if you like that 'lemon substitute' thing.
(Why not, lemons are expensive!)
There are many many early determinate reds out there, suitable for a 4 ft hoop. Small ones will fit for sure, and even a medium sized determinate may be okay if it's really cool - this makes them stay more compact for sure. OTOH it may be warm in that hoop!
If I were you I'd follow Vladimir's advice and try the ones that are seriously cold tolerant.
For me, both Stupice and Moravsky Div would be considered quite tolerant of cool weather, they are really reliable for us and set a great load at daytime highs between 60-70 F, slower setting but not bothered by colder days where the high is 50-59 F. But they are indeterminate so a 4ft hoop is not really suitable.