The speedy 23-year-old winger joined Bromley in May 2017 having joined from Wrexham.
Allen`s (pictured) previous clubs include Yeovil Town, Torquay United and Aldershot Town.
Stones have also signed powerful centre-back Ian Gayle from league rivals Welling United.
The 25-year-old has had EFL experience at Dagenham & Redbridge as well as a host of loan spells in non-League football with the likes of St Neots Town, Grays Athletic, Kingstonian, Histon, Whitehawk and Bishop`s Stortford.
After being released by the Daggers at the end of the 2015/16 season, he signed for Braintree Town, where he made twenty-two appearances, joining the Wings this season.
Both centre back Glen Wilson and winger Alan O’Brien sustained problematic injuries during the Buildbase FA Trophy win over Hereford FC at The Vale on Saturday.
O’Brien, who had only just made a return from the treatment room, suffered a reoccurrence of his troublesome hamstring problem and is likely to be out long-term.