They are from 'Racing 2000' on E-bay (where else, I refuse to use Amazon) described as "2" 52mm Universal Car LCD 7 Colour Oil Press Pressure Gauge Meter Psi with Sensor". There are a number of gauges for all comers from these folk & as far as I can ascertain they are within reasonable tolerance, or at least those that have been through my hands. I can check temperature & pressure with a degree of ease & accuracy in the workshop & I've had nothing grossly misleading, although initially I couldn't get a sensible reading on the oil temperature being lower than expected & indicated by my I/R thermometer. I used a simple +1 adaptor to link into the oil filter housing & the temperature gradient up this rather long adaptor was affecting the results, (I can be a right old fanny when it comes to accuracy). I replaced it with a pancake adaptor between filter & housing, ( see 'a thread sandwich') & forgot about the "O" ring, which isolated the ground. A proper ground restored & all was well. I hope this helps, sometimes I can spend an inordinate length of time looking for the right thing for me at the right price & to be able to pass that info on to save others that time & effort is oddly rewarding.
M