Tangye Superline Bottle Jacks

"Base fitted for optional gauge and accessories"

Still quite expensive!.

However; Ive got a normal bottle jack at home... it has a screw is 'release' valve... similar to a trolley jack... (you turn it when you want it to go down).

well; just an idea... could you not fit a guage to that port? perhaps even engineer a t-peace to maintain the release functionality at the same time?