Only ones I can think of are old Italeri sets. There was one in US Marines set, and a couple stretcher bearers in the US Support Troops set. They were both old and pretty bad. Tamiya had a set as well that went with their Landrover Ambulance kit as well, also old and pretty bad. There are some in resin from Warriors and a few others that I can't remember the name of. Check the above sites and they should come up.
Good luck.
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