I think you may have to bite the bullet and wear a size larger jeans.
And thus make the D-lock holster redundant when the jean can't hold you up without a belt.
I did the same, normal size fit perfectly but a bit tight on the thigh, one size bigger is perfect but required a belt.
@edscoble started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
And thus make the D-lock holster redundant when the jean can't hold you up without a belt.
I did the same, normal size fit perfectly but a bit tight on the thigh, one size bigger is perfect but required a belt.