Hi Bykee, is it the spring and latch that doesn’t work or is the bottom tube stuck on the locking latch? If the bottom tube is stuck on the latch then loosening the two bolts, re-positioning the latch and tightening the bolts may solve your problem. Locktight on those two bolts is important and do not over tighten them.
If you need to replace the locking latch I do stock them as BlackStridaAustria provided a link.
Cheers, Bill Wilby