I think you can fine some of what you are looking for at Edsel Vila's place on J. Armando Berm?dez, about a long block from 27 de Febrero. It is across the street from a Moto Shop.
Another place is Bici Center, across the street from Ferr. Ochoa on Bartolom? Col?n, in the Jorge Plaza. Next to a computer store I think.