My "refurbish plan" will be to install new seals in the rotating areas and supply new O-rings for the dowels, along with a set-to-minimum-clearance dustoff of the internal clearances, where possible. If necessary, I can bore and re-bush the shaft holes, but I have not seen much wear there, so far. This stuff will all reduce the in-pump leakage. One thing that's kept me from it, so far, is that big screen seal situation. I may have to offer them with some sort of caveat about that. 
One other thing to check: look at your oil pressure relief bolt in the oil filter. If it has been relieving pressure/flow from time to time, you will see movement marks where it compresses the spring and the piston slides up. If there are no marks anymore (like mine) then it is not developing sufficient excess flow. This generally indicates that it's not doing a good job on a hot day in heavy stop-and-stop traffic, and the engine will get balky from the extra heat.
I am not finding OEM dowel Orings. Do you have them? and what "seals in the rotating areas" do you mean? I've seen only larger Orings for the 2 end covers.
I'll check the bolt. Several pumps on ebay with "buy it now" sub-$25. Tempting to chance it. If nothing else, I'd have a cheapo to experiment with.
I bought a bunch of the right size O-rings at a local seals outlet, Rocket Seals, in Denver. If they don't have it in stock, it's rare: if it's made, they can get a minimun order size for $35. So, I got a bunch of $35 orders last summer from them.
There is a small oil seal on the shaft that runs through the pump. It's an odd size by -0.5mm, or about .020" undersized. To install the standard seal, a slight groove must be cust, about .010" to .020", into the pump pbody where that seal rests, so the standard seal can be clicked into place. Fortunately, the shaft IS a standard size, just the pump cutout was not, back then.
Between the 2 thin O-rings and this seal, most of the leakage out of the pump can be stopped: they get as hard as plastic over time, and leak. The sides of the rotors wear off the plates of the pump body and covers, generating internal leaks. This damage shows up as scored sides on the rotors and plates. This can be resized by cutting back the rotors slightly to reduce the volume of the pitting, then cutting back on the housing edges to space the cover closer again. The cover might need some thinning, too, or a new one can be made or substituted in.
The flow is nearly linear: if you narrow the rotor 1%, the flow drops 1%. But, since they are already much more worn than this, and leaking, the net result is an INCREASE in flow and pressure. This has been done in car engines since I was a kid, and works very well. Today, of course, you can just go out and buy most car pumps: it wasn't like that in the 1950s and '60s.
Fortunately for us all, Honda was overly concerned with oil flow in these engines, and the pumps oversupply considerably. On midget racer engines I saw in the early 1970s, two in particular, that were made from the 750 Honda, both used the stock oil pump (sans transmission), driven from a machined takeoff on the cam. This is only 1/2 crank speed, at the resulting pressure was over 100 PSI. The second engine had a 2:1 gearbox arrangement fitted to the pump end, fed from the main galley on the back of the engine, and ran about 60 PSI. Both were faster than the stock engine runs the pump, as it is driven by a 4.(something):1 stepdown from the primary drive, off the kickstarter gear.
My only slowdown so far in making these reburb pumps available is: I'm an engineer. I won't sell them to someone until I have a fixture where I can do a "before & after" measure of the improvements, and sell something tangible...
