LEFTYS

You are not likely to find used T150's as they did not exist until this 3rd generation release of T-series irons. You might find some 1st and 2nd generation T100 or T100S sets. One of the best places to look is www.2ndswing.com

Fellow lefty as well. Definitely harder to find the gently used item at a reasonable cost. There is the Titleist certified site, www.titleistcertified.com/

and i like to check 2nd swing.
www.2ndswing.com/.../left-handed-stiff-steel-38dot0in-d-52438364610

LH Titleist irons are not common. With a 2 year cycle and the percentage of iron sets that are custom, the generation 3 T150 irons will be few and far between. Unlike other OEMs with annual releases, there isn’t a big surge of turning over irons every spring.

Global golf, 3Balls, and Dallas Golf are other sites. With caution to do your homework, eBay is another option.

I recommend saving up and get a fitting. Being the latest model, a good used set of T150's isn't going to save you that much money. If you're playing T150's you probably have a good game, and trying to find a used set, especially left hand, you don't want to settle on a shaft, lie angle, or length that doesn't fit your swing.

2ndswing has some

Some good suggestions here, I have also seen a few sets get posted on some of the lefty golf facebook groups that I’m a member of. Decent pricing too, though beware of scammers, if it seems to good to be true, it is, and use a service like PayPal that offers buyer’s protection.