This spurred me into creating the first of these pencil-marker charts, using my full set of 150 Prismacolors and 96 Tombow pens. I was able to create 60 comparative shades which doesn't sound like a lot but I was actually surprised to find that many! As with all conversions they are not 100% matches - there will be slight differences in colours depending on how many layers of marker you use, for example. So, this is the closest I could get and I hope it's helpful for you all! As with all my resources this chart is completely free for download, just click the button below and print. The file is a PDF and includes both the blank chart for you to colour yourself, and a full-colour reference chart which I personally coloured and scanned.
Please let me know in the comments if you found this useful!