John
No affiliation with the seller but just seen this listed on Ebay and it may just kick start your collection. A mixture of good and bad but if it is just a representative display then it may help. The globe and laurel looks like it could be white metal which would fill the gap for Royal Marine Police (unfortunately I would say it is a copy)
https://www.ebay.co.uk/itm/WW2-ROYAL...MAAOSwck1dZp~j
Paddy