There is no filler pipe and both valve covers are connected to what appears to be a crank case breather affair.
If there is no other obvious place to use as a 'filler', can you use the breather for filling?
The breather hoses connected to the valve covers drain directly from the valve covers into the sump. It might be a slow process, but once a year / 3000 miles is not like having to do it all the time.
A note on refilling: You have a 'big' 2 liter engine capable of relatively high RPM compared to smaller stock-ish motors. You might find best success filling to 1/2 quart low (between the high and low marks on the dip stick). Your spyder has plenty of extra oil capacity beyond the normal stock VW engine case. (You have an extended extra capacity sump, plus you have another quart in the filter. So in a sense, you won't end up 1/2 quart low but more like 2 quarts high plus whatever is in the remote oil cooler). For whatever reason, I have found that if I fill my 2332 to the top fill line on the dipstick, in short order it will find a way to push oil out until it gets to about 1/2 quart low, where it will stay happily until the next oil change. If I fill to 1/2 quart low to begin with, it will stay there for the duration until next change. It might be that the 2332cc pump overwhelms the volume of the case designed for 1600cc and relatively lower RPM. Maybe increasing the air volume in the case by 1/2 quart makes it happy; I don't know. But that is my experience.