Not very familiar with those models, but I can post the pronto hex which should work perfectly. 30 sec skip is enabled by a specific button sequence and is not a specific command per se. Can you load pronto hex into your remote? Otherwise any JP1 remote from this list works fine. All are made by UEI who also make Comcast remotes.[Link: hifi-remote.com]
The Xsight and Nevo are most similar to your MX's.
Your existing X1 remote can shoot IR if you unpair it first:[Link: remotecentral.com]Older Comcast 1067BX3 remotes shoot IR for the X1 as well, if you're interested in picking up one of those. But getting good learns of XMP protocol which the X1 uses is nearly impossible.
Here's our X1 device which you can use with Remote Master and IRScrutinizer to generate your own pronto hex:[Link: hifi-remote.com]
(must create account to download)