🚀 go-pugleaf

In an article mentioned here "Building the 2 meter cube radio" in which a
RS weather radio is converted to recieve 2 M it was mentioned that a crystal
filter in the front end would be a nice inprovement.  My question is this;
has anyone seen or does anyone know of such a filter for a 2M reciever.
Any advice on how to design or lift such a circuit would be appreciated.  I
have built made the changes to that cube and it was quite satisfying but
the selectivity was not to great. I assume that the purpose of a crystal 
filter would be to make the reciving band more narrow and thus more selective.

Thanks in advance for your help.