Another low-cost brifter option for Shimano drivetrains is MicroShift / MicroNew.
7-speed brifters at $53 here:
https://www.amazon.com/Micronew-Shif.../dp/B00XSOCD1Y
When I needed to replace the original brifters on this Marin, I ordered a set of R9's for right around $55. Quality at install seemed quite good. I wouldn't hesitate to use them again, especially when I couldn't find any brifters from Shimano at that price.