D&D-original monsters printed in the Bestiaries 1-4:
Aboleth, Ankheg, basidirond, bebelith, behir, black pudding, boggard, bulette, chuul, cloaker, dark creeper, dark stalker, darkmantle, drider, ettercap, froghemoth, gelatinous cube, girallon, goblin dog, grey ooze, nessian hell hound, intellect devourer, mephit, mimic, mite, ochre jelly, otyugh, owlbear, phase spider, pseudodragon, purple worm, remorhaz, retriever, roper, rust monster, sahuagin, shambling mound, shocker lizard, stirge, vargouille, vegepygmy, violet fungus, xill, xorn, yellow musk creeper; achaierai, akata, aranea, athach, aurumvorax, azer, belker, blindheim, blink dog, carnivorous blob, crysmal, dark slayer, destrachan, forlarren, frost giant, gloomwing, gray render, grick, grig, grippli, gryph, hangman tree, Inevitables, korred, krenshar, locathah, magma ooze, mercane, mongrelman, necrophidius, neh-thalggu, quickling, quickwood, phycomid, skulk, slithering tracker, giant solifugid, albino cave solifugid, tendriculos, tenebrous worm, tentamort, thoqqua, viper vine, winterwight, yrthak; adherer, allip, ascomoid, demilich, demodand, dire corby, disenchanter, dragonne, flail snail, flumph, guecubu, huecuva, kamadan, kech, magmin, rot grub swarm, giant rot grub, phantom fungus, black mastiff, spider eater, thriae, tojanida, wolf-in-sheep's-clothing; dark caller, dark dancer, death dog, lurking ray,
More to the point, if you can't find it on d20pfsrd, chances are that no 3pp has converted them, yet, though you could always check the Tome of Horrors.
