The Cottonian Chronicle for the year 1093 notes:

Res filius teudur a francis qui in brecheniauc habitabant occiditur (Gough-Cooper, c414.1).

Translation: Rhys ap Tewdwr was killed by the French who were inhabiting Brycheiniog (Remfry,211).

A sixteenth century source, (NLW Mostyn 212b, 129) adds further information:

ar bedwredd vlwyddyn o wladychrwydd William Goch vrenin Lloyger i lladded y Bleddyn hwnn gida Rys ap Tewdwr ymrw-wydyr y Battail garllaw glann Wysc trwy ryfel Barned Nywmark a Syr Reinallt Awbre ar marchogion Ffrengig erraill (Bartrum, 130).

Translation: In the fourth year colonization of William the Red, King of England, Rhys ap Tewdwr was killed at the battle of Battail near the banks of the River Usk in the war between Judge Nwymark and Sir Reynold Awbre and the other French knights

This places the conflict on the banks of the River Usk near the village of Battle, North West of Brecon (Bartrum, 130). `Site of Battle (A.D. 1092)? is marked on historic and modern Ordnance Survey mapping at SO 0070 3088, to the west of the village and near the river Ysgir, a tributary of the Usk, but on what authority is unclear. Nothing else is recorded for this event.

RCAHMW (Battlefields Inventory), Dec 2016

Bibliography
Bartrum, P. C., `Maelda Hynaf and Ednywain ap Bradwen?, Bulletin of the Board of Celtic Studies, 20/3 (1963), 236-9.
Gough-Cooper, Henry (ed.) The Cottonian Chronicle: Annales Cambriae, The C Text from London, British Library, Cotton MS Domitian A. i, ff. 138r?155r, online edition.
Remfry, Paul M. Annales Cambriae: A Translation of Harleian 3859: PRO E. 164/1: Cottonian Domitian, A1: Exeter Cathedral Library MS.3514 and MS Exchequer DB Neath, PRO E. 164/1 (Castle Studies Research, 2007).