From what I have read, most third-declension Latin adjectives other than comparatives take the i-stem endings -ī, ium and -ia in the ablative singular, genitive plural and neuter nominative/accusative plural, respectively.
Allen and Greenough §114-119 discuss the general patterns, and Allen and Greenough §121 discusses -e vs. -ī in the ablative singular, -ium vs. -um in the genitive plural, and a few other variations like -īs vs. -ēs in the masculine/feminine accusative plural and feminine nominative singular forms in -a, like clienta and hospita.
Adjectives that take -a in the neuter plural nominative/accusative appear to be even less common than adjectives that take -um or -e, though. It seems that many third-declension adjectives of one ending lack attested neuter plural forms at all (discussed to some extent in Allen and Greenough §122); of those that have them, I have only been able to find the following that decline as consonant stems in this form:
the class of comparative-declined adjectives, such as neuter plural nominative/accusative adjectives ending in -iōra (including maiōra/majōra) and minōra
plūra (despite genitive plurium). It seems pluria was maybe a very uncommon variant form, but the typical form was plura. The derived word complura/compluria apparently exists in both forms.
ūbera. Of course, this exists as a plural substantive, but according to Allen and Greenough §119, it also exists as a neuter plural adjective (although the ablative singular form of this adjective is usually ūberī). Wiktionary gives "ūberia", but that form doesn't show up anywhere in the PHI Latin Texts corpus, so I'm guessing Wiktionary is just showing an incorrect declension table for this word.
Are there any more?
I have found an old book ("Some improvements to the art of teaching...," Fifth Edition, by William Walker, 1693) that also mentions compound adjectives ending in -corpora or -colōra, like bicolōra, but it seems to say that these actually originated as o-stem forms (corresponding to masc. singular nominative -corporus, -colōrus), not as consonant-stem forms.