Glenn Phillips will also stand in for Kieron Pollard at Welsh Fire for the whole of the competition due to injury
The Hundred squads 2021: Full men's and women's player lists
Colin de Grandhomme and Marchant de Lange are the latest additions to The Hundred ahead of the competition's grand lift-off next week.
New Zealander De Grandhomme, who has played for Hampshire in the LV=Insurance County Championship and T20 Blast, has been signed to replace Andre Russell at Southern Brave due to his West Indies commitments and travel complications caused by the Covid-19 pandemic.
"When I got the call to join Southern Brave it was an easy decision," said De Grandhomme.
"I’ve settled in really well at Hampshire and I’m hoping to create some more fantastic memories at the Ageas Bowl. I’m really looking forward to linking up with Devon Conway again and all of the guys can’t wait to get going.”
Somerset quick De Lange will replace Wahab Riaz, who was turned away from the UK last week due to a work permit issue and will not return, at Trent Rockets.
Kieron Pollard has also been ruled out due to injury, with Gloucestershire's overseas player Glenn Phillips - already enlisted to replace him at Welsh Fire until he arrived - now signed up for the entire campaign.
Ollie Pope has been confirmed to miss the start of The Hundred for Fire as he recovers from a thigh injury but England hope he will be available for the India Test series which starts on August 4.