So: Buying my sweet new rain tray from 914Rubber was cool except for the fact that rain was still getting in my engine compartment due to the fact that my rain tubes were rotten and broken. I'd gone to Home "Despot" several times looking for a good replacement with no luck. I finally bought 20 feet of Koi Pond tubing on Amazon that seems to fit and work very nicely. I used about four feet of it for my two 914's, and I have about 15 feet left -- enough leftover for 5 pairs (assuming about 16 inches per tube -- the originals seem to be around 15 inches). If anyone wants a pair of 16 inch tubes, PM me and I'll send a pair for $7. These seem to work very well, but they are vinyl. I am not 100% sure they'll fully stand up to engine bay heat over time, but I've used them for several days so far with no issues.
If you prefer to buy 20 feet worth, here's the Amazon ad: Pond Tubing
A couple of pics (note: funnel not included):
Click to view attachment
Click to view attachment