Lewis & Short

istim, adv. [iste], thither, to that place (very rare): nolite, hospites, ad me adire! ilico istim! Enn. ap. Cic. Tusc. 3, 12, 26 (Enn. Trag. v. 404 Vahl., and Trag. Rel. v. 303 Rib., isti, in the same meaning): quod eos usque istim exauditos putem, Cic. Att. 1, 14, 4 (Klotz, but Baiter reads istinc): ite istim, ecferte lora, Plaut. Capt. 3, 4, 125 (acc. to Lachm. ad Lucr. vol. 2, p. 189; al. istinc).