First, I want to thank the amazing folks on Thingiverse who have designed and posted some amazing spool holders for the Replicator 1 to hold Octave spools of filament, which are available for cheap on Amazon.
However, in my experience, I was not able to get a final printed example that worked very well. When I did get one to print, it didn't do a very good job of holding my spools. There was a lot of sagging of the spool, and some of the spool holders wouldn't fit into the hole on the back of my Replicator. Some of them wouldn't print right because there was too much undercut which required support. Some of them even required me to print out multiple parts and GLUE them together! Maybe it is just me, but I didn't buy a 3D printer so I could glue pieces together! ;)
Overall, I was not satisfied with the selection I found. I was frustrated.
But I need a couple of really good spool holders.
So what did I do? Well, I'm a "maker"...so I built them myself!
The spool holder "thing" presented here is designed from scratch in Autodesk Inventor (if you haven't played with Autodesk Inventor, get it...it is awesome...you can use it at TechShop for free, and you can get a free copy that you can use on your own computer for 6 months for free if you are a TechShop member!)
I didn't attribute by spool holder to any other Thingiverse members, but that's because I literally took my own measurements from the printer and the spools and designed it myself in about 10 minutes.
This "thing" is designed to print really well with the acetone/ABS slurry technique (to prevent curling) that I pioneered which you can search for here and on Inventables.
This part requires no raft or support at all, and is very sturdy to hold a heavy spool full of brand new filament. I printed it (and most everything I make) with 1 shell and 100% fill with a 0.17mm layer height.
Even though there is an offset, the offset is designed in so that you can print the spool holder without support flat on the bed. This spool holder works on either the right or left side, but if you really want symmetry, you can mirror this part and print it for the left spool of your Replicator. I didn't bother.