There's always eBay.ph: 4PCS Nichicon MUSE KZ Audio Capacitor 1000uF 25V NEW (item 250505140694 end time Jan 25, 2010 22:40:50 PHT)
It would be interesting to know the difference, Nichicon do several caps in the "Muse" range. Try "Nichicon muse 1000uf" in google. (interesting, the packaging is aklmost identicle to the Elana's) Also, it seems the RJJ spec is a high reliablity thing. beyond that i have no idea what a cap change might offer.
Oh yeah, the Elna RJJs are 105C rated. The Nichicon Muse KZs in the eBay link are only 85C. I think that the temperature rating relates to the reliability factor by operating longer at higher temps. That's just an educated guess on my part.
Both the Elna RFS SILMIC II and the Nichicon Muse KZs are taller than the RJJs and apparently of greater diameter.