The midfielder has been at the Foxes since joining from Liverpool back in 2021, with the club fending off the likes of Manchester United to secure his signature.
Not 19 until November, he has already featured 23 times for their U21s in the Premier League 2 this season and comes highly recommended by those at the King Power Stadium.
The teenager becomes the club's fourth arrival in the last seven days, with forward Harry Wakefield, defender Kieran Fenton and attacking midfielder Jordan Hallam also agreeing terms with the Lions.
He goes straight into contention for Saturday's game against fellow strugglers Bradford Park Avenue at Greenwich Avenue, with Basford going in search of just their third league win of the season.
Discussing Lewis' arrival, manager James Jepson said: “Jack is a midfield player who comes highly recommended by both Lee Tomlin and Adi Yussuf, two friends of mine at Leicester.
“He gets about the pitch with an eye for a pass and is competitive – it’s an area we currently need support in. We’ll have him until January 1 and he’s a fantastic signing for us.
“With Jack, and like any of our other signings, we have options to come in, but we back the boys and want to give them the opportunity.
"However, if there’s a chance to bring people in and replace, then that’s what we’ll have to do to get us out this situation.
“Unfortunately, that’s how football works when you’re at the bottom end, but we have to keep it positive, and it provides competition for shirts which is something we need right now.”