Shimano Adjustable Crank Arm Length I currently run Shimano 105/Ultegra/Dura-Ace (2X11) components on my road bike.

Chain Dura-Ace
Cassette &amp; Crank 105
Derailleurs Ultegra

I am looking to replace my cranks when I wear out my next chain and want to experiment with different crank lengths (e.g 165, 170, 172.5, and inbetween etc.) without buying extra Shimano Cranks for $$$. I also want to make the jump up to 53/39 from 50/34 that is on there now.
I know Shimano does not make any adjustable length crank arms.
Do I have any off the shelf options to be able to use my other Shimano components and possibly use a 3rd party crank to get adjustable cranks without spending tons more than what I would on a Shimano Crank set?
Thanks
---- Update
I'll probably go about trying to see if I can rent or try out a crank arm for a bit to ensure the fit is good and then buy the full ultegra crankset. Just as a bit of a follow up does anyone know if you can buy the right side crank arm on for an ultegra crank set new as I see the left side sold separately, but not the right?
Thanks
There are sizing cranks that are primarily used by fitters. They're expensive and heavy and usually intended for a fit machine more than going on an existing bike. Ones I'm familiar with are square taper so getting them on to modern bikes would involve jumping through some hoops, but there may be a 24mm one out there.
Trying all the lengths in a short amount of time and with minimal contrivance would be a good thing to find a fitter's help with. Crank length and saddle fore-aft are numbers that play off each other, so you want to get your fore-aft dialed at the same time if you can.