The RHO-Lens for the Headplay is brilliant, but I thought that there would be a better to insert the lens & hold it. Each time I tried to install it, I would end up with finger marks on the lens.
So here is my answer to the problem, a lens holder that is held in position where the orginal headplay lens was.
On the four lens holder tabs is a piece of double sided tape to hold the lens in place, then the lens holder plate is screwed into place with four M2 x 6mm screws.
To get the lens in the correct position, insert the lens holder into the bottom half the Headplay first and then rest the RHO-Lens on the nose bridge and push down onto the double sided tape.
The RHO-Lens is from here: http://rho-lens.com/index.html