Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
purchase [ˈpəːtʃɪs] n поку́пка#; (grip etc) захва́т
vt покупа́ть (купи́ть*perf)
to get a purchase on ухва́тываться (ухвати́ться*perf) за +acc
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.