I think [name_u]Jazz[/name_u] is pretty neat ^^ There’s also [name_u]Perry[/name_u]. And [name_u]Jay[/name_u], or with the right middle you could use the initials, JC or JD or something?
[name_m]Jax[/name_m] just reminds me of [name_m]Jaxon[/name_m] so it really diminishes [name_m]Jasper[/name_m] for me.