Reddit mentions of Your Own Big Bed

Here's what we got, and my son really liked them:

Big Bed for Giraffe

Big Enough for a Bed

Your Own Big Bed

I'd keep doing what you're doing - talking up how great the new room is, making it sound like such an obviously better choice, DUH how would ANYONE choose the old nursery over this AWESOME big kids room! I like the idea of letting him be involved in decorating it (pick out some decals, posters, whatever). Maybe look at some options and then the deal is that if he starts sleeping in the new room, you'll buy whatever item you've chosen together.

I'd say go for it tonight, give it your best shot ("we're going to have an extra special story tonight to celebrate sleeping in our special new bedroom!"), and if he's really not up for it just say okay, we'll try again tomorrow, maybe you'll feel more ready then. Remind him that when he starts sleeping there he'll get X, but that there's no hurry, his room is waiting for him whenever he's ready. It sounds like you're doing everything right; I think pushing too hard could definitely backfire and make the process harder than it needs to be.

Edited to add -- not sure if you're also transitioning from a crib to a bed as part of the new room, but if you are, you could try reading him some books on that theme - for example this one or this one.