Any left and/OR right open carry holsters?

Rather than go get 2 different holsters, are there any good ones that can be worn either side? There will be times when I carry left-handed instead of right, and other-way-round.

Yes and no.
Yes there are holsters that are ambidextrous. No they are not that good a quality.
I have at least one in my collection that is ambidextrous and has a removable belt clip that lets me use OWB and IWB and has a reversible thumbsnap strap. I use it for my Taurus 85.

I would suggest a leather slide holster. They sell one at the NRA store for around $20 bucks which can also be used as an IWB holster. Another option might be a 3 slot holster that you can wear strong side or cross draw but that depends on your reason for wanting to carry on either side.

my reason for left-side carry sometimes, is due to nerve damage/tendon issues with my "strong" right hand. There are times when it flares up enough that it becomes difficult to operate the pistol properly with my right hand. I usually know 1st thing I wake in the morning if that hand is going to be functional that day- so on those days, I'd carry left-side.
I do this with pocket pistols already in CCW.
But, I've always made it a habit to practice shooting either hand- in case of something like this, or injury to/loss of use of, the strong hand. I alternate when practicing- 1 mag right hand, next mag left hand, etc. That practice has long since paid off.

In your case the cross draw wont help you much. I think I would suggest a leather slide holster, or if you want a thumb break uncle mikes makes a nice nylon slide holster with a break. I agree its a good thing to practice with either hand. I have even practice drawing my weapon with my weak side from the strong side holster which requires use of the body to support the handgun while quickly switching around your grip. But priceless if your strong side hand is out of the fight.

I have a Bagmaster holster that's ambidextrous.

The retention straps can be switched, too - there's one that's stiff & one that's just a strap, so you'd want the thumb to push against the stiff one to unsnap it.
It has sturdy, wide, nylon belt loops for 2 sizes of belt.
I got one w/ a mag pouch, but they come without too.

The straps are velcroed for the bottom 3" or so, with hook velcro on the outside of the belt loops, so you can adjust them up & down & canted fore or aft to fit several sizes of gun.

I'll email you a picture if you want; PM me your address.

is this in leather? and the strap-is it functional for Condition One carry-hammer cocked?