I don't know any dedicated package but a while ago I used some TikZ Code to create keys for my HP-12C. Maybe you can use this and align it in a keyboard layout style.
\documentclass[12pt]{scrartcl}
\usepackage[]{amsmath}
\usepackage{tikz}
\usetikzlibrary{positioning,shapes,shadows}
\tikzstyle{abstract}=[rectangle, draw=black, rounded corners, fill=gray!20,drop shadow, text centered, text=black, text width=8mm]
\tikzstyle{fkey}=[rectangle, draw=black, rounded corners, fill=orange,drop shadow, text centered, text=black, text width=8mm]
\tikzstyle{gkey}=[rectangle, draw=black, rounded corners, fill=blue!40,drop shadow, text centered, text=black, text width=8mm]
\newcommand{\mykey}[2]{%
\begin{tikzpicture} \node (Item) [abstract, rectangle split, rectangle split parts=2]
{\textbf{\scriptsize{#1}} \nodepart{second}\textbf{\tiny{#2}}};%
\end{tikzpicture}}
\newcommand{\myfkey}{%
\begin{tikzpicture} \node (Item) [fkey, rectangle split, rectangle split parts=2]
{\textbf{\footnotesize{f}} \nodepart{second}};%
\end{tikzpicture}}
\newcommand{\mygkey}{%
\begin{tikzpicture} \node (Item) [gkey, rectangle split, rectangle split parts=2]
{\textbf{\footnotesize{g}} \nodepart{second}};%
\end{tikzpicture}}
\begin{document}
\mykey{n}{$12x$}
\mykey{SST}{$\Delta \text{DYS}$}
\myfkey
\mygkey
\mykey{Enter}{=}
\end{document}
