At the forefront of the campaign is Jyotsna Mehta, whose husband, Bharat, 46, was murdered in his Archway, north London, Post Office last month.
The culprit is still at large, although police have several leads and hope for responses to a photofit picture of one of Mr Mehta's three assailants.
The Post Office in conjunction with the National Federation of Sub-Postmasters has offered a reward of pounds 25,000 for information leading to an arrest.
Under the Post Office's standard insurance scheme Mrs Mehta will probably receive about pounds 60,000.
At the moment, Britain's 20,000 sub-postmasters are expected to provide their own cameras and panic buttons to supplement the standard grille provided by the Post Office.
Michael Coney, representing the North London Sub-Postmasters Federation was among hundreds of mourners at Mr Mehta's funeral last Thursday.
He has survived two armed raids on his Tottenham premises and has been trying for years to persuade the Post Office to provide video cameras.
'It would greatly increase the feeling of safety, both for me and my staff. I am sure all sub-postmasters would say the same.'
However, the Post Office is unsure of how effective cameras and panic buttons would have been in preventing Mr Mehta's murder.
'Generally speaking, standards of security are quite good, Bert Bertoloni, the general manager of Post Office Counters Ltd, said.
'If there are lessons to be learned from this tragedy, we want to learn them. But it is not clear that the automatic provision of security is always a key factor.
Local sub-postmasters act as agents for the Post Office and own their premises.
A spokeswoman for the Post Office said yesterday that Post Office security was a matter for the sub-postmaster and local managers of Post Office Counters Ltd.
'We do provide more than the standard grille. But we cannot go into details for security reasons, she said.
Mr Mehta's family, however, is not convinced that these measures are enough and yesterday in a statement welcomed the demand for more security.
'If this happens, perhaps the brutal death of Bharat Mehta, who embodied a generous, non-violent respect for all forms of life, will not have been totally in vain.
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