Close coupled cistern toilet seat posts loose_any suggestions valued

My toilet seat (retaining) posts have become loose, but being close coupled cistern, have no access to what I presume are some form of plastic wing nuts underneath.
I gather you can now get top loading fixing sets for loo seats, so would like to fit those after I get current posts out, so I can use the cistern holes. eg
Anyone any suggestions as to either how as short term fix, make posts tighter, with no access underneath? They became loose when prying seat off the 2 posts.
2nd option would be to get out/ break off, but without damaging porcelain, or having to remove whole cistern unit, which may damage floor tiles?
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