FPT
Swagelok SS-QC4-D-400 1/4", Straight-Connector, FPT – Pipefittings
You will find that 1/4 in is a common size in hardware stores.
1 In. X 1 In. X 3/4 In. Black Iron Reducing Tee
You will appreciate how the RMN5073B fits into your existing workflow without changes.