I know this board mainly deals with fountain pens, but I would never have found it had I not received a few nice rollerball pens a while back. One was a Pentel Excalibur RX15 which has been permanently discontinued. I have not had much luck finding the discontinued Pentel Refills (BFL5BP-K6) at a reasonable price. I have tried a few that looked similar, but they protrude too far out of the barrel at the tip. Do any of you happen to know a suitable and available refill? Thanks so much