No recommendations 'cause I still need one, but I'm seriously considering building one. I've got the capability to cut, heat, bend, and thread metal with a medium amount of experience and lots of time. I'm gonna' give it a try and if I screw it up I will have lost nothing but my time and a few pieces of scrap laying around. Doesn't look too complicated.
I saw a video of a fella removing and installing a front sight on an M&P using a padded c-clamp to fasten the slide to a table. He then used a trimmed wooden dowel to drive the old sight out and install the new one. Seemed to work like a champ, he took his time and got it right with not a scratch on the weapon.