These symbols are available from the Miscellaneous panel on the Symbol toolbarSymbol_toolbar.tex:
dtbpF110.4375pt248.1875pt0ptmisc.wmf
You can enter some miscellaneous symbols with the keyboard shortcutsKeyboard_shortcuts.tex
itbpF38.875pt24.5pt6ptindex.wmfindex.texEntering mathematicsindex.tex#Entering mathematics, Miscellaneous symbolsindex.tex#Miscellaneous symbols, Symbol panelsindex.tex#Symbol panels, Symbol toolbarindex.tex#Symbol toolbar, Symbolsindex.tex#Symbols