Hi kwaw -- beware that some will think the word "roman" means having to do with Rome, but "roman" here is the French word, the English word is "romanesque" - which of course refers vaguely to 11th - 12th-ish century european architecture and sculpture, preceding (and sort of overlapping) the so-called gothic period.
Also beware of image web-searches that show you everything but the kitchen sink because there is a vague key-word in common. Not all of those posted are modillons, and not all are from Sainte Radegonde. A modillon specifically is a figure holding up a cornice.
Actually, I have photographed all the hundred some odd modillons of the interior of Sainte Radegone (and dozens of other French churches). In Sainte Radegonde, there are some delightfully salacious ones ... (dogs licking their .. ahem ... nun displaying her .. ahem, etc.) (but I won't post those here ...) (however, perhaps on my blog, or whatever).
So I don't think the aquarius from Issoire is really a modillon. There are figures from the whole zodiac all around the outside of the church. But funny you should mention Issoire, I have just come back from Issoire, in Auvergne, which is one of the very most interesting we have seen so far, from the point of view of the amazingly well-preserved (and beautifully painted and restored) capitals (chapiteaux) inside the church. - we (my husband and I) have become rabid fans of romanesque sculpture. Everywhere we go we find a few other people taking photographs who are equally fanatical about the subject. Very dangerous territority for those already with a tendancy to collect things like .... TAROT CARDS. (joke)