As far as I know, not off the shelf. So your skills and abilities to
Look at the problem
Use your mental CAD ,figure out what you need and scrounge up the stuff to build it. It's well within the rules to buy the long pedal and work from there. Are you planning on the platform instead of the peg?
Go Stare at the shifter
Let how it works go through your eyes and Think about how to accomplish what you want.

https://hotvehs.com/what-is-a-motorcycle-heel-toe-shifter/

It doesn't seem like a technically difficult thing.
Buy or build the parts, unless you want the platform instead of the peg.

What kinda footwear are you using?

If your shifter is out beyond your toe when you have the heel up against the peg,maybe get a shifter and have it shortened to put the rubber on top of your big toe?
Before I try to solve it, let me know what is going on. And No, hunting for the shifter is way not safe. You need to be able to operate the shifter without delay. I'm finally Seeing a couple of potential answers, but I need to know more.

If you put the arch of your foot on the peg and slide your foot forward till the heels hits the peg,toes pointed straight forward, not out,what happens?

I've seen foot boards on a V-Star 650. it looked normal on it.

I started riding when I was 11, and my first bike was a 60cc Yamaha with a heel toe shifter.  My tiny feet rested between the tabs and every shift required a foot shift either forward or back.
Forward to adulthood, and I have owned two bikes with heel toe shifts, and now I have to decide which end to rest my weight on.  This is annoying too.
If you really want one... I suggest measuring the output shaft diameter,.. and going to a dealer and finding one from another bike with the same.
... but,.. sit on it and feel where your foot will rest.
You need Shaq size feet to rest on both.
Maybe you need a shorter shifter?  In which case... do the same.
Go to a dealership and find a bike with a shifter that fits yer' foot.

I'm not trying to talk you out of what you want,... but I've ridden a lot of bikes over 50 years, and heel toes annoy the heck out me personally.
... my riding buddy, on the other hand loves them.

So what do I know?...

I saw a cool universal hand shifter for motorcycles on Amazon the other day.  But these are not for everyone , most people crash before they get it down

There are several ways to do a hand shifter, plenty of choppers have “jockey shifters”, they call them this because you have to reach behind your leg to shift.

Another solution I saw on a trike ridden by a paralyzed guy was to place a clutch lever on the shift handle. Worked well for him.  

Indians and Harleys before the late 1950’s had left foot clutches, so the shift lever was fairly straightforward to use.

If you want a right hand shift, no clutch lever relocation would be needed, although the linkage could get complicated fast.

For the original poster, have a look at the heel toe shifter on a Royal Enfield Meteor. It’s simple bent steel, and wouldn’t be too difficult to fabricate something similar. They don’t have footboards, either.