A passive cock-ring can generate a firmer erection if your erections are a bit on the soft side. These are more gentle than the pump constriction rings. Durex pleasure ring is an example.
There are lots of cheap vibrating cock rings, if they do anything for you. (They're usually disappointingly underpowered, and the battery goes flat before you get there, but maybe they work for someone.)
A good male toy is the Hot Octopus Pulse (which used to be called the Guybrator). It is a male vibrator which can be used with or without an erection, which is a key point for men unable to get an erection, and it might help generate an erection if there's some level of ED or no libido. There are 4 in the range, with or without remote control, and with (Duo) or without (Solo) a separate clit stimulator on the other end.
There are fleshlights (which I think are passive devices - no built-in vibrator).