Godox released a ton of Fujifilm compatible flashes earlier this year and they have been pretty much universally praised by photographers since launch. These very reliable and affordable flashes can do HSS + TTL without a problem on the Fujifilm X-T2 and GFX, plus they will be on sale through the end of Cyber Monday at least. While I haven’t personally used Godox flashes on my equipment I have friends that shoot Godox and haven’t had an issue with them yet.
Flashpoint 600 for Fuji (Save$200): Adorama
Godox VING V860IIF TTL Lithion ION + X1T-F TTL (Save 10%): B&H Photo
Godox TT350F Mini Thinklite TTL (Save $4.20): B&H Photo
Godox TT685F Thinklite TTL Flash + X1T-F Trigger (Save 10%): B&H Photo
Godox AD200 TTL Pocket Dual + X1T-F Trigger (Save $42.30): B&H Photo
Godox AD200 TTL Pocket Flash + X1T-F Trigger (Save $23): B&H Photo
Godox AD200 TTL Pocket Flash (Save $20): B&H Photo
Godox X1T-F TTL Wireless Flash Trigger (Save 5%): B&H Photo