Specifically one in particular, my dad spent years making it, creating maps for it, etc. and we’d really like to see it featured on something popular like critical role or similar. How could I go about showing it to different DnD influencers to see if any of them are interested?
Most d&d podcasts and shows get a bunch of free stuff that they feature (dice, minis, dice towers, stuffed animals, drawings of their characters, etc).
I doubt they buy things that someone wants to sell them.
You probably have to choose: do you want to sell it, or do you want to see it featured?
If the latter, then probably send a letter with some pictures, asking if they would feature it if you had it shipped, to whoever you want (most shows and podcasts advertise a PO Box or some such). If they answer such things on their show, chances are they’ll give you a shout out and let you know on an episode. If they say yes, then you ship it to them, and that’s… It.