I'm looking for a broad nib to put into one of my little ringtops, and I notice a #75 nib available on the Interweb. Before I throw my money in the street I thought I'd ask if anyone knows if a #75 nib would fit into one of these wee little pens? How about a Warranted #4 - broad flex? One wants to buy the nib, then find a pen for it.