Cyrillic blackboard bold

Question

Is there a way to produce blackboard bold Cyrillic letter?

(I know I can do Greek letters with mathbbol, but I need $\mathbb{Л}$.)

Answer 1

Not really pretty, but unless you find an open shape Cyrillic font, I see not much more to do.

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[russian]{babel}
\usepackage{amsmath}

\DeclareRobustCommand{\bbel}{%
  \mathord{\text{%
    \ooalign{%
      Л\cr
      \hidewidth\kern0.125em I\hidewidth\cr
    }%
  }%
}}

\begin{document}

$x\bbel y^{\bbel}$

\end{document}

Answer 2

For the particular symbol you mention you could fake it by adding a vertical rule to the symbol either to the left or right of the main vertical stem or (egreg's suggestion) print a capital I close to the symbol or double print the symbol with a small separation

\documentclass{article}

\usepackage[utf8]{inputenc}
\usepackage[russian]{babel}

\begin{document}

Л

$\mbox{Л\kern-0.4em\vrule height 1.55ex depth 0ex width 0.08em}$

$\mbox{Л\kern-0.05em\vrule height 1.58ex depth 0ex width 0.08em}$

$\mbox{Л\kern-.15emI}$

$\mbox{Л\kern-0.9emЛ}$

\end{document}

But really one should go back to metafont and make a proper set of symbols.