I ran this last year and this is what I did. Just get the pdf and adjust the size and resolution you want in photoshop (or whatever) and import into VTT.
As an aside to the OP, some advice. As I said, I just reran this campaign, and I ran into some things. First is that Carl Sargent really hated PCs lol. In fact, he literally spells it out several times that PC need to run away or they will all die. This happens a lot in the campaign. You know your players, so decide if you need to adjust encounters to fit how they play. For example, if you have players that won't have fun running away all the time, you might want to adjust them, or implement more opportunities for the PCs to recruit allies within the caverns. Second, if you prefer a hack and slash old school approach, the campaign is just fine. But if you want more story driving plots and continuity, you may have to do some extra DM pre-work to tie in everything together. Many encounters seem like they only exist as XP dispensers, and that's it. This is especially true in Book II.