Possibility of new stable charged particles is discussed in VIA lecture by Maxim Khlopov
http://viavca.in2p3.fr/maxim_yu_khlopov.html
Cosmoparticle physics of new generations in ppt presentation of VIA lecture by Konstantin Belotsky
http://viavca.in2p3.fr/kostia_ppt.ppt
New stable generations from the approach unifying spins and charges in the VIA lecture by Norma Mankoc-Borstnik
http://viavca.in2p3.fr/norma_mankoc_borstnik.html
Charged Planckean objects - daemons in VIA lecture by Edward Drobyshevski
http://viavca.in2p3.fr/edward_m_drobyshevski.html
The Physics of Quarks: New Research (Horizons in World Physics, Volume 265) - you can find there the paper about 4th stable quark
https://www.novapublishers.com/catalog/product_info.php?products_id=7484
Record of discussion at the 11 Bled Workshop "What comes beyond the Standard model"
http://viavca.in2p3.fr/conclusion_bled08.html