If you need the jaws for drilling the blanks, because you have no other option, you may be out of luck. (I'm not sure.)

In that case, look at a different check or the least expensive way to drill maybe 5-6" of stock.

There are lots of options like this:
https://www.amazon.com/Manoch-Aluminum-Universal-Workbench-Drilling/dp/B07NY9N6L5

But you obviously get what you pay for. Aligning and keeping the drill parallel to your stock will likely be a challenge, and you'll need a vise, ideally optimized for blanks, to hold what you're drilling.

Specialty tools like this exist, though I'd never buy another thing from Penn State Industries. Worst customer experience I've ever had.

https://www.pennstateind.com/store/DRILLBA2.html

Rockler makes one that is more feature-rich, but it's $300. At that price point, you might be able to find a drill press with a tilting table (I haven't looked) so the only attraction would be portability. Here's a page that shows without the vice ($189, which is still quite expensive IMHO for this tool) and you can also see a model with fewer features, and the one with the integrated vise (which you can buy separately if you want to upgrade the base model later) for $299.

https://www.rockler.com/rockler-portable-drill-guide

You can also get very cheap drill presses if you just want to drill pen blanks. Again, you get what you pay for. I've made the mistake of buying the cheapest, only to upgrade later, more than once. You end up paying more in the end, but sometimes needs must.