Labome VAD database does not indicate that any TWIST1 antibody has been used in Xenopus embryos. If you can not find any reference, you might check with Abcam about ab50887. It has been used very extensively. Based on Abcam website, it is made with a recombinant human fragment, it can be a good candidate for you if this fragment is shared between human and Xenopus.
LifeSpan Bio indicates that their rabbit anti-TWIST pAb is cross-reactive with Xenopus, based on BLAST analysis of the immunogenic peptide. Here is their datapage: