With only minor changes to the actual electrode pattern, I have made the ESD design much more compact, which will reduce the cost by over 33%. The total cost for two boards is now $327. I am going to purchase them with Steve's card tomorrow.
I have made a first draft of the design for the ESD (see PDF below). The electrode comb spacing is 0.2", which should be roughly what we want for objects ~1-3" in size.
Sunstone offers boards printed on Rogers 4350 material as part of their fast and cheap QuickTurn service. This is a glass- and ceramic-based material that is designed for RF applications, but I have seen some examples of it being used at UHV in some ion trapping experiments. Since our vacuum doesn't have to be outrageously good (and the lab isn't clean enough for that anyway), this ought to work fine.
The finish will be silver (gold would be preferable for oxidation purposes, but Sunstone only offers silver with this service---otherwise we'd have to submit a much costlier and time-delaying custom order).
I have designed the ESD such that there are two holes offset horizontally from the center of the plate. These are for the passage of the measurement beam. I chose off-center because most modes' signals should be weaker at the center from symmetry. I chose to put two in for no particular reason other than symmetry, again. NOTE: we will have to drill these holes ourselves.
The electrodes will be connected to the HV supply by soldering to relatively large plates on the back side. One will be connected to the (positive, single-sided) HV amp output, while the other will most likely be connected to a wire that is bolted to the chamber (earth) at the other end.
It was not clear from the quote page, but apparently the RO4350 material is a little pricier than the standard FR4. For two of these boards, the cost is $493.35 ($246.68 /ea.). I think this is reasonable---assuming it works---considering how fast we can get it.
If no one has any objections or comments, I will put the order in.