FWIW, when I got mine from ebay, I showed it to one of the machinists at work and he said that a local machine shop (we're not set up to do that type of work) could produce the "holder" portion with relatively little effort.
I thought it might be worth it to make a few that were compatible with readily available US dial gauges so others could either use their existing indicators or find an indicator at a lower cost. I might still be willing to do this...
As far as renting the tools out, there was a VW place that used to rent out the "hub shark" tool for doing wheel bearings in this fashion.
I think you had to give them a credit card # as a deposit for the cost of the tool ($220 or so) and then the rental was $20 or something with the purchase of the bearings. I believe there was a time limit on the rental before they'd run your card for the cost of the tool.
While it'd be nice to be able to offer a "timing tool kit" to people with the lock pin, cam lock and dial indicator, I'm not sure how to do it without getting burned if the tool gets broken, misplaced or not returned in time. Normally, individuals aren't setup to process credit cards and I guess there's a trust issue there.
For me, I just broke down and bought some tools and borrowed others. I figure if I'm going to work on the D's, I should have the right tools to do it with. That and I'm a tool geek.