I was going to advise you that my old one is not suitable if you work on a variety of bikes as I do- but it sounds what you want. Cradled at the bottom bracket with an arm going up under the Downtube. My problem is that I bought it 10 years ago when steel bikes were the rule and I now have fat tube Aluminium bikes and the clamp for holding the downtube does not fit.
See attachment- but where you can get one- I have no idea.
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How long was I in the army? Five foot seven.
Spike Milligan