The gt28 has been used for a long time in the Vw world and is well respected but with many Chinese copies so be careful of tha eBay bargain.
i believe there may be a twin scroll turbo smaller than the efr 7064 as that would be too big for the power you want, it may be worth asking Mark Shead as that would be a huge benefit but suspect it will cost a lot and maybe not go small enough. The Borg efr is quite a moder turbo.