If you deleted the air injection pump and converted to the shorter 133 tooth timing belt, then do you have the special tension adjusting tool for the 138 tooth belt? If "yes", are you interested in selling it?
On to the main point. I'm late to this thread, so I hope you had the matter resolved long ago. But just for the record...
You have the choice of a spring-loaded, semi-automatic tensioner that was stock on Elite-Eclats of that period, or the eccentric tensioner that was used from 1986-onward. You may have to change the front seal housing to be compatible with your choice, but it's all 'possible' with Lotus parts.
If you go with the period-correct spring-loaded tensioner, then be aware that it got off to a troubled start, and went through a series of changes... there were six versions in total. For those who have early cars with the first tensioners, take care of them, and don't ignore maintenance!! Other than that, I'm not trying to create any paranoia.
But if you're out to buy one, then buy the newest version you can find find. The latest and best was used on the early, 1980-85 Turbo Esprit, as well as other Lotus cars of that same period. It has the Nylatron plastic piston, as well as replaceable plastic bushings in the hinge. Pass over any tensioners with the metal piston and a metal-to-metal hinge (no replaceable bushings).
A907E0913K, Last version, used on 1980-85 Turbo Esprit. Hex head adjuster screw.
Note part NUMBER change... 0913 Vs 0893 below, and 0855 below that:
B907E0893K, as used on late A/C equipped Elite & Eclat. Replaced:
A907E0893K, new version used on late Elite-Eclat (in both my '78 & '79 Eclats).
Note part NUMBER change... 0893 Vs 0855 below.
C907E0855K, which replaced B907E, which replaced A907E (Earliest & least desireable).
I like the spring-loaded tensioner. In theory, it's better than the non-compliant eccentric tensioner. However, it's a mechanism, and requries maintenance. It had a troubled early history, but many of the early problems were due to owners ignoring them until they broke. The later versions can take more neglect, and the critical hinge wear points are rebuildable... just replace the plastic bushings. Without the bushings, hinge wear means throw away the tensioner.
But if you're not good at maintenance, then you should consider the eccentric tensioner. The eccentric tensioner still needs maintenance, but less "mechanical" maintenance on the tensioner itself. While the semi-automatic tensioner can compensate for belt stretch, the eccentric can't. So, with the eccentric you'll find it necessary to periodically check and re-set the timing belt tension. You've traded tensioner maintenance for belt tension maintenance. Choose between tensioner types... but avoiding 'belt' maintenance all together is NOT a choice on 9XX engines!
All Lotus tensioners use the same bearing.
The best place to shop for out-of-production tensioners is probably Lotusbits in the UK. They specialize in used/ salvage parts. They can sell one to you in as-is condition, and you rebuild it. Or they can rebuild it for you at extra cost.
Lotus Excel parts, Lotus Esprit parts and Lotus spares, new and used
I hope you had your Eclat running last Fall, and have enjoyed driving it.