Optical mounts can be expensive pieces of hardware with precision alignment in mind, especially for larger aperture items. This is a low cost, lightweight, minimum occlusion holder for 1mm x 2" optics (e.g. https://www.thorlabs.com/thorproduct.cfm?partnumber=EBS2 ).

Tension/mounting hole is 4mm and is well suited for use with M3 or 4-40 hardware.